Further investigation shows that [realNumber](http://hackage.haskell.org/package/base/docs/src/GHC.Read.html#readNumber) is used for Read instance of Int.

I think what happened is that when the leading parser input can be parsed as a floating number, it will do so and commit to that decision, making backtracking impossible.

I do understand that Read just need to be able to parse whatever Show can produce and is not designed to deal with raw inputs, but this is still a surprising behavior to me.

When I'm using Text.ParserCombinators.ReadP, I really appreciates it that I can use `readP_to_S read` to parse simple values (integers and floating points in particular),

but it bothers me that parsing Int from "123.aaa" is fine but "123.1aa" will fail simply because the not-yet-consumed part of input is different.